#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
ambari_jinja2.loaders
~~~~~~~~~~~~~~

Jinja loader classes.

:copyright: (c) 2010 by the Jinja Team.
:license: BSD, see LICENSE for more details.
"""

import os
import sys
import weakref
from types import ModuleType
from os import path

try:
  from hashlib import sha1
except ImportError:
  from sha import new as sha1
from ambari_jinja2.exceptions import TemplateNotFound
from ambari_jinja2.utils import LRUCache, open_if_exists, internalcode


def split_template_path(template):
  """Split a path into segments and perform a sanity check.  If it detects
  '..' in the path it will raise a `TemplateNotFound` error.
  """
  pieces = []
  for piece in template.split("/"):
    if (
      path.sep in piece
      or (path.altsep and path.altsep in piece)
      or piece == path.pardir
    ):
      raise TemplateNotFound(template)
    elif piece and piece != ".":
      pieces.append(piece)
  return pieces


class BaseLoader(object):
  """Baseclass for all loaders.  Subclass this and override `get_source` to
  implement a custom loading mechanism.  The environment provides a
  `get_template` method that calls the loader's `load` method to get the
  :class:`Template` object.

  A very basic example for a loader that looks up templates on the file
  system could look like this::

      from ambari_jinja2 import BaseLoader, TemplateNotFound
      from os.path import join, exists, getmtime

      class MyLoader(BaseLoader):

          def __init__(self, path):
              self.path = path

          def get_source(self, environment, template):
              path = join(self.path, template)
              if not exists(path):
                  raise TemplateNotFound(template)
              mtime = getmtime(path)
              with file(path) as f:
                  source = f.read().decode('utf-8')
              return source, path, lambda: mtime == getmtime(path)
  """

  #: if set to `False` it indicates that the loader cannot provide access
  #: to the source of templates.
  #:
  #: .. versionadded:: 2.4
  has_source_access = True

  def get_source(self, environment, template):
    """Get the template source, filename and reload helper for a template.
    It's passed the environment and template name and has to return a
    tuple in the form ``(source, filename, uptodate)`` or raise a
    `TemplateNotFound` error if it can't locate the template.

    The source part of the returned tuple must be the source of the
    template as unicode string or a ASCII bytestring.  The filename should
    be the name of the file on the filesystem if it was loaded from there,
    otherwise `None`.  The filename is used by python for the tracebacks
    if no loader extension is used.

    The last item in the tuple is the `uptodate` function.  If auto
    reloading is enabled it's always called to check if the template
    changed.  No arguments are passed so the function must store the
    old state somewhere (for example in a closure).  If it returns `False`
    the template will be reloaded.
    """
    if not self.has_source_access:
      raise RuntimeError(
        f"{self.__class__.__name__} cannot provide access to the source"
      )
    raise TemplateNotFound(template)

  def list_templates(self):
    """Iterates over all templates.  If the loader does not support that
    it should raise a :exc:`TypeError` which is the default behavior.
    """
    raise TypeError("this loader cannot iterate over all templates")

  @internalcode
  def load(self, environment, name, globals=None):
    """Loads a template.  This method looks up the template in the cache
    or loads one by calling :meth:`get_source`.  Subclasses should not
    override this method as loaders working on collections of other
    loaders (such as :class:`PrefixLoader` or :class:`ChoiceLoader`)
    will not call this method but `get_source` directly.
    """
    code = None
    if globals is None:
      globals = {}

    # first we try to get the source for this template together
    # with the filename and the uptodate function.
    source, filename, uptodate = self.get_source(environment, name)

    # try to load the code from the bytecode cache if there is a
    # bytecode cache configured.
    bcc = environment.bytecode_cache
    if bcc is not None:
      bucket = bcc.get_bucket(environment, name, filename, source)
      code = bucket.code

    # if we don't have code so far (not cached, no longer up to
    # date) etc. we compile the template
    if code is None:
      code = environment.compile(source, name, filename)

    # if the bytecode cache is available and the bucket doesn't
    # have a code so far, we give the bucket the new code and put
    # it back to the bytecode cache.
    if bcc is not None and bucket.code is None:
      bucket.code = code
      bcc.set_bucket(bucket)

    return environment.template_class.from_code(environment, code, globals, uptodate)


class FileSystemLoader(BaseLoader):
  """Loads templates from the file system.  This loader can find templates
  in folders on the file system and is the preferred way to load them.

  The loader takes the path to the templates as string, or if multiple
  locations are wanted a list of them which is then looked up in the
  given order:

  >>> loader = FileSystemLoader('/path/to/templates')
  >>> loader = FileSystemLoader(['/path/to/templates', '/other/path'])

  Per default the template encoding is ``'utf-8'`` which can be changed
  by setting the `encoding` parameter to something else.
  """

  def __init__(self, searchpath, encoding="utf-8"):
    if isinstance(searchpath, str):
      searchpath = [searchpath]
    self.searchpath = list(searchpath)
    self.encoding = encoding

  def get_source(self, environment, template):
    pieces = split_template_path(template)
    for searchpath in self.searchpath:
      filename = path.join(searchpath, *pieces)
      f = open_if_exists(filename)
      if f is None:
        continue
      try:
        contents = f.read().decode(self.encoding)
      finally:
        f.close()

      mtime = path.getmtime(filename)

      def uptodate():
        try:
          return path.getmtime(filename) == mtime
        except OSError:
          return False

      return contents, filename, uptodate
    raise TemplateNotFound(template)

  def list_templates(self):
    found = set()
    for searchpath in self.searchpath:
      for dirpath, dirnames, filenames in os.walk(searchpath):
        for filename in filenames:
          template = (
            os.path.join(dirpath, filename)[len(searchpath) :]
            .strip(os.path.sep)
            .replace(os.path.sep, "/")
          )
          if template[:2] == "./":
            template = template[2:]
          if template not in found:
            found.add(template)
    return sorted(found)


class PackageLoader(BaseLoader):
  """Load templates from python eggs or packages.  It is constructed with
  the name of the python package and the path to the templates in that
  package::

      loader = PackageLoader('mypackage', 'views')

  If the package path is not given, ``'templates'`` is assumed.

  Per default the template encoding is ``'utf-8'`` which can be changed
  by setting the `encoding` parameter to something else.  Due to the nature
  of eggs it's only possible to reload templates if the package was loaded
  from the file system and not a zip file.
  """

  def __init__(self, package_name, package_path="templates", encoding="utf-8"):
    from pkg_resources import DefaultProvider, ResourceManager, get_provider

    provider = get_provider(package_name)
    self.encoding = encoding
    self.manager = ResourceManager()
    self.filesystem_bound = isinstance(provider, DefaultProvider)
    self.provider = provider
    self.package_path = package_path

  def get_source(self, environment, template):
    pieces = split_template_path(template)
    p = "/".join((self.package_path,) + tuple(pieces))
    if not self.provider.has_resource(p):
      raise TemplateNotFound(template)

    filename = uptodate = None
    if self.filesystem_bound:
      filename = self.provider.get_resource_filename(self.manager, p)
      mtime = path.getmtime(filename)

      def uptodate():
        try:
          return path.getmtime(filename) == mtime
        except OSError:
          return False

    source = self.provider.get_resource_string(self.manager, p)
    return source.decode(self.encoding), filename, uptodate

  def list_templates(self):
    path = self.package_path
    if path[:2] == "./":
      path = path[2:]
    elif path == ".":
      path = ""
    offset = len(path)
    results = []

    def _walk(path):
      for filename in self.provider.resource_listdir(path):
        fullname = path + "/" + filename
        if self.provider.resource_isdir(fullname):
          for item in _walk(fullname):
            results.append(item)
        else:
          results.append(fullname[offset:].lstrip("/"))

    _walk(path)
    results.sort()
    return results


class DictLoader(BaseLoader):
  """Loads a template from a python dict.  It's passed a dict of unicode
  strings bound to template names.  This loader is useful for unittesting:

  >>> loader = DictLoader({'index.html': 'source here'})

  Because auto reloading is rarely useful this is disabled per default.
  """

  def __init__(self, mapping):
    self.mapping = mapping

  def get_source(self, environment, template):
    if template in self.mapping:
      source = self.mapping[template]
      return source, None, lambda: source != self.mapping.get(template)
    raise TemplateNotFound(template)

  def list_templates(self):
    return sorted(self.mapping)


class FunctionLoader(BaseLoader):
  """A loader that is passed a function which does the loading.  The
  function becomes the name of the template passed and has to return either
  an unicode string with the template source, a tuple in the form ``(source,
  filename, uptodatefunc)`` or `None` if the template does not exist.

  >>> def load_template(name):
  ...     if name == 'index.html':
  ...         return '...'
  ...
  >>> loader = FunctionLoader(load_template)

  The `uptodatefunc` is a function that is called if autoreload is enabled
  and has to return `True` if the template is still up to date.  For more
  details have a look at :meth:`BaseLoader.get_source` which has the same
  return value.
  """

  def __init__(self, load_func):
    self.load_func = load_func

  def get_source(self, environment, template):
    rv = self.load_func(template)
    if rv is None:
      raise TemplateNotFound(template)
    elif isinstance(rv, str):
      return rv, None, None
    return rv


class PrefixLoader(BaseLoader):
  """A loader that is passed a dict of loaders where each loader is bound
  to a prefix.  The prefix is delimited from the template by a slash per
  default, which can be changed by setting the `delimiter` argument to
  something else::

      loader = PrefixLoader({
          'app1':     PackageLoader('mypackage.app1'),
          'app2':     PackageLoader('mypackage.app2')
      })

  By loading ``'app1/index.html'`` the file from the app1 package is loaded,
  by loading ``'app2/index.html'`` the file from the second.
  """

  def __init__(self, mapping, delimiter="/"):
    self.mapping = mapping
    self.delimiter = delimiter

  def get_source(self, environment, template):
    try:
      prefix, name = template.split(self.delimiter, 1)
      loader = self.mapping[prefix]
    except (ValueError, KeyError):
      raise TemplateNotFound(template)
    try:
      return loader.get_source(environment, name)
    except TemplateNotFound:
      # re-raise the exception with the correct fileame here.
      # (the one that includes the prefix)
      raise TemplateNotFound(template)

  def list_templates(self):
    result = []
    for prefix, loader in self.mapping.items():
      for template in loader.list_templates():
        result.append(prefix + self.delimiter + template)
    return result


class ChoiceLoader(BaseLoader):
  """This loader works like the `PrefixLoader` just that no prefix is
  specified.  If a template could not be found by one loader the next one
  is tried.

  >>> loader = ChoiceLoader([
  ...     FileSystemLoader('/path/to/user/templates'),
  ...     FileSystemLoader('/path/to/system/templates')
  ... ])

  This is useful if you want to allow users to override builtin templates
  from a different location.
  """

  def __init__(self, loaders):
    self.loaders = loaders

  def get_source(self, environment, template):
    for loader in self.loaders:
      try:
        return loader.get_source(environment, template)
      except TemplateNotFound:
        pass
    raise TemplateNotFound(template)

  def list_templates(self):
    found = set()
    for loader in self.loaders:
      found.update(loader.list_templates())
    return sorted(found)


class _TemplateModule(ModuleType):
  """Like a normal module but with support for weak references"""


class ModuleLoader(BaseLoader):
  """This loader loads templates from precompiled templates.

  Example usage:

  >>> loader = ChoiceLoader([
  ...     ModuleLoader('/path/to/compiled/templates'),
  ...     FileSystemLoader('/path/to/templates')
  ... ])
  """

  has_source_access = False

  def __init__(self, path):
    package_name = f"_ambari_jinja2_module_templates_{id(self):x}"

    # create a fake module that looks for the templates in the
    # path given.
    mod = _TemplateModule(package_name)
    if isinstance(path, str):
      path = [path]
    else:
      path = list(path)
    mod.__path__ = path

    sys.modules[package_name] = weakref.proxy(
      mod, lambda x: sys.modules.pop(package_name, None)
    )

    # the only strong reference, the sys.modules entry is weak
    # so that the garbage collector can remove it once the
    # loader that created it goes out of business.
    self.module = mod
    self.package_name = package_name

  @staticmethod
  def get_template_key(name):
    return "tmpl_" + sha1(name.encode("utf-8")).hexdigest()

  @staticmethod
  def get_module_filename(name):
    return ModuleLoader.get_template_key(name) + ".py"

  @internalcode
  def load(self, environment, name, globals=None):
    key = self.get_template_key(name)
    module = f"{self.package_name}.{key}"
    mod = getattr(self.module, module, None)
    if mod is None:
      try:
        mod = __import__(module, None, None, ["root"])
      except ImportError:
        raise TemplateNotFound(name)

      # remove the entry from sys.modules, we only want the attribute
      # on the module object we have stored on the loader.
      sys.modules.pop(module, None)

    return environment.template_class.from_module_dict(
      environment, mod.__dict__, globals
    )
